Method of manufacturing optical-quality polarized part incorporating high-impact polyurethane-based material

ABSTRACT

Optical-quality polarized parts and methods for manufacturing the optical parts are disclosed. The optical-quality polarized parts comprise a high impact, lightweight, high optical quality polyurethane construct and a polarizer bonded to the construct. The construct may be a lens substrate wherein the polarizer is integrally bonded at or near the front surface of the lens substrate. A sidefill gasket may be used to support and position the polarizer within a mold cavity for reproducibly forming the optical part. The polarizer may comprise a polyethylene terephthalate film or a laminated polyvinyl alcohol film or wafer. The polarized optical part- has improved impact resistance over conventional thermoset resin parts, as well as better optical properties than similarly impact-resistant polycarbonate constructs.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of U.S. patent application Ser.Nos. 09/569,479 filed May 12, 2000; 09/567,711 filed May 10, 2000;09/475,424, filed Dec. 29, 1999; and 09/447,445 filed Nov. 22, 1999,each of which is hereby incorporated by reference as if fully set forthherein.

BACKGROUND OF THE INVENTION

[0002] The field of the present invention relates to the use of highimpact, lightweight, high optical-quality polymeric material inpolarized plastic parts such as eyewear.

[0003] Optical-quality eyewear requires good optical performance. In theselection of lens materials for use in optical-quality eyewear, thecolor, weight, and safety of the material is important, as well as goodoptical performance. Most often, however the respective properties ofdifferent materials necessitate trade-offs among the desired lenscharacteristics. For instance, glass, has very good optical properties,but it is heavy (a dense material) and only impact resistant if thick(resulting in an even heavier lens). Polymeric thermoset resins, such asCR-39®, are lighter in weight but are lacking in impact resistance.Polycarbonate, in contrast, is both lightweight and highly impactresistant. Polycarbonate also has a high refractive, index. Thus, thinlenses can be made utilizing polycarbonate. However, polycarbonateexhibits more chromatic aberration than glass, typically resulting inunacceptable off-axis distortion.

[0004] In light of the foregoing, an alternate material with both goodoptics and high impact resistance is desirable. In addition, alightweight material is desired for the wearer's comfort, convenience,and fashion consideration.

[0005] U.S. Pat. No. 5,962,611 (“'617 patent”) describes an initialformulation of a prototype material, which the inventors recognized mayprovide an improved combination of lens characteristics. This materialcomprises polyurethane pre-polymer compositions, the reaction product ofsuch pre-polymer compositions, and the diamine curing agent used intheir reaction. While this material may offer improved lenscharacteristics over conventional materials, the inventors noted that ithas too much residual yellowness for an acceptable standard ophthalmiclens. In addition, when the inventors worked with the disclosedprototype material to try to manufacture lenses, they noted that it doesnot have sufficient structural integrity to maintain an accurate opticalpower when surfaced with standard optical grinding, polishing, andedging techniques.

[0006] Due to the foregoing deficiencies, in order for the prototypematerial disclosed in the '617 patent to be an acceptable lens material,the inventors had the formulation modified (hereinafter “modified highimpact polymeric material”). In particular, the inventors added dyes orcolorants to obtain the specific requirements of a standard ophthalmiclens. The inventors also added stabilizers to protect the polyurethanecomponent of the disclosed material from oxidation. Finally, theinventors modified the disclosed material's chemistry and componentratios to improve its structural integrity.

[0007] As shown in Table 1, the modified high impact polymeric materialcompares quite favorably with conventional optical lens materials in itscombination of physical properties. Notably, the modified high impactpolymeric material exhibits very low birefringence. This property is anespecially useful attribute in combination with polarizers. Briefly, thepolarizer in optical-quality eyewear has been aligned to preferentiallyremove most of the glare (plane polarized reflections) from horizontalsurfaces. If a material has a high degree of birefringence (that is, ifits crystal structure causes incoming light to be polarizedsignificantly differently along different crystal planes), it willaffect the apparent efficiency of a polarizing lens. If a birefringentmaterial is now placed in the light path before the polarizer, some ofthis plane-polarized light will be redirected into other orientationssuch that the polarizer alignment will not block as much of the incominglight. The result is that the lens will be far superior to a tinted lensin blocking glare (since tinted lenses have no preferential absorptionor reflection for plane polarized glare), but it will also not be asefficient as a lens without birefringent materials.

[0008] After modifying the prototype material disclosed in the '617patent and analyzing its physical properties, the present inventorsrecognized that their modified high impact polymeric material couldpossibly be used in the manufacture of improved optical-quality plasticparts. The present inventors also recognized that if their modified highimpact polymeric material could be combined with a polarizer, they mightbe able to provide the marketplace with improved polarized eyewear. Suchoptical-quality polarized parts, include, but are not limited to,semi-finished, finished prescription and non-prescription lenses,facemasks, shields, goggles, visors, and display of window devices.

[0009] Initial tests, however, lead the inventors to believe that theirmodified high impact polymeric material could not be utilized tomanufacture optical-quality polarized plastic parts. In early attemptsto combine their modified high impact polymeric material with standardpolyvinyl alcohol (PVA) polarized film using conventional techniques,the film was consistently displaced and bent out of shape during theintroduction of the material. Thus, initial testing revealed that asubstitution of their high impact material for standard lens thermosetresin materials and conventional manufacturing processes was notpossible.

[0010] Analysis of the initial testing further revealed that theproperties of their modified high impact polymeric material greatlycontributed to the inventors' failure to incorporate it into an improvedoptical-quality, polarized plastic part. Briefly, casting of polarizedlenses and other eyewear requires controlled and reproduciblepositioning of the film or supported polarizer within the solidifyingpolymer. Gasket designs and certain conventional filling techniquestypically help to control the positioning of the film during standardlens casting. It is not uncommon to spend 10 to 15 seconds filling theassembly with resin to ensure even flow and controlled distribution ofthe resin around the polarizer layer. However, their modified highimpact polymeric material solidifies more quickly than standardthermoset resins (approximately 30 seconds rather than several hours).Thus, standard PVA polarized film was consistently displaced and bentout of shape during the introduction of the material due, at least inpart, to the quick setting time of the material.

[0011] In a similar manner, the polarization or other essential physicalproperties of standard polarizing film can be compromised by the heat ofthe polymer's solidification process or by reaction with the monomers ofthe pre-mix. The modified high impact polymeric material createsconsiderable heat within the mold assembly during its normal, exothermiccuring process. This can soften the polarizer or supporting layers,causing further displacement of the polarizing film. Depending on thepolarizers or polarizing materials used, this heat could also change thecolor or decrease the efficiency of a polarizer. Organic dyes used aspolarizers would be especially susceptible to this type of damage.

[0012] Thus, the inventors recognized that existing manufacturingprocesses suggested that high impact polyurethane-based material couldnot be used to effect an optical-quality plastic part due to thefundamental difficulty of handling the fast-reaching modified highimpact polymeric material, in combination with the more demandingprocess of reproducibly positioning a polarizer within any opticalconstruct, while maintaining the optical and mechanical performance ofthe part. If high impact polyurethane material could be incorporatedinto an optical-quality plastic part, a desirable product would beeffected.

SUMMARY OF INVENTION

[0013] The preferred embodiments relate to optical-quality polarizedparts and to methods of manufacturing such optical parts comprising ahigh impact, lightweight, high optical quality polyurethane-basedmaterial and a polarizer. The polarized optical part advantageously hasimproved impact resistance over conventional thermoset resin parts, aswell as better optical properties than similarly impact-resistantpolycarbonate constructs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The various objects, features and advantages of the presentinventions may be better understood by examining the DetailedDescription of the Preferred Embodiments found below, together with theappended, figures, wherein:

[0015] Table 1 shows a comparison of different materials' physicalproperties relevant to optical applications, including the inventors'modified high impact polyurethane-based material;

[0016]FIG. 1 shows an optical-quality polarized part constructedaccording to a preferred embodiment, wherein the part comprises a highimpact polyurethane-based optical lens substrate and a polarizerintegrally bonded to the lens substrate;

[0017]FIG. 2 shows a detailed view of the integral bond between thepolarizer and the lens substrate illustrated in FIG. 1;

[0018]FIG. 3 is a flowchart illustrating a method of manufacturing anoptical-quality polarized part according to a preferred embodiment andparticularly a, method of one-sided fill of the optical part;

[0019]FIG. 4 is a flowchart illustrating a method of manufacturing anoptical-quality polarized part according to a preferred embodiment andparticularly a method of two-sided simultaneous fill of the opticalpart;

[0020]FIG. 5 is a flowchart illustrating a method of manufacturing anoptical-quality polarized part according to a preferred embodiment andparticularly a method of two-sided sequential fill of the optical part;

[0021]FIG. 6 is a flowchart illustrating a method of manufacturing anoptical-quality polarized part according to a preferred embodiment andparticularly a method of bonding a polyethylene terephthalate (PET)polarizer to a preexisting solid optical construct;

[0022]FIG. 7 illustrates a top view of a side fill gasket, as disclosedin U.S. patent application Ser. No. 09/447,445, that may be used toeffect an optical-quality part according to a preferred embodiment; and

[0023]FIG. 8 illustrates a side view of the side fill gasket, shown inFIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The preferred embodiments will now be described with respect tothe drawings. To facilitate the description, any numeral identifying anelement in one figure will represent the same element when used in anyother figure.

[0025]FIG. 1 illustrates an optical-quality plastic part 100,particularly a polarized lens, comprising a high impact, lightweight,high-optical quality polymeric construct 102 and a polarizer 104 bondedthereto. The part 100 has been manufactured according to one of theembodiments as disclosed and illustrated herein such that the polarizer104 may be “integrally bonded” (interpenetrated bonding or bonding atthe molecular level) to the optical construct or lens substrate 102.Advantageously, the optical-quality plastic part 100 has improved impactresistance over conventional thermoset resin parts, as well as betteroptical properties than similarly impact-resistant polycarbonateconstructs.

[0026] Turning in detail to FIG. 1, polarizer 104 is a polarizing filmbonded near the front surface 106 of the lens substrate 102. Polarizer104 may alternatively be bonded at the front surface 106, however, beingbonded near the front surface 106, film 104 is interposed between firstand second members 108 a, 108 b of substrate 102. First and secondmembers 108 a and 108 b may be either discrete parts, or liquid monomeror polymer mixtures that are placed in contact with the polarizer andallowed to solidify. In this manner, the first member 108 a of the lensmaterial 102 protects the film 104 such that there may be no need tohardcoat it. However, to protect the first member 108 a from abrasionand undue wear, member 108 a may optionally be hardcoated. As the hardcoating 112 is optional, it is shown in dashed lines.

[0027] Both sides of the polarizer 104 may be surface treated, eitherphysically and/or chemically, to effect an integral bond 120 between thefilm 104 and the second substrate member 108 b and an integral bond 122between the film 104 and the first substrate member 108 a. Bonds 120,122 are shown in detail in FIG. 2.

[0028] The high impact, lightweight, high-optical quality construct 102preferably comprises a polyurethane-based material, comprising apolyurethane pre-polymer reacted with a diamine curing agent. Such ahigh impact polyurethane-based material is disclosed in the '617 patent,which patent is incorporated herein by reference as if fully set forthherein. As the '617 patent indicates, the polyurethane-based materialmay be prepared by first producing a prepolymer by reacting oneequivalent of a polyester glyclol or a polyether glycol having a weightaverage molecular weight of between about 600 and about 1200 with4,4′-methylenebis(cyclohexyl isocyanate) in an equivalent ratio of 2.5to 4.5 NCO for each OH, with a preferable ratio of about 3 to 3.5 NCOfor each OH. The prepolymer is then reacted with an aromatic diaminecuring agent such as 4,4′-methylenebis(3-chloro-2,6-diethyl)benzamine inan equivalent ratio of 0.95 to 1.02 NH₂/1.0 NCO.

[0029] The high impact, lightweight, high optical quality construct 102more preferably comprises a modified version of the prototype materialdisclosed in the '617 patent. The inventors prefer their modified highimpact polyurethane-based material because the prototype materialdisclosed in the '617 patent has too much yellowness and insufficientstructural integrity for an acceptable standard ophthalmic lens. Themodified high impact polymeric material particularly comprises up to 12molar percent trimethylol propane in the prepolymer to improve materialstiffness, rather than the lower 4-8% disclosed in the '617 patent. Forophthalmic lens materials, the same preferred aromatic diamine curingagent is reacted with the prepolymer in an equivalent ratio of 0.9 to1.1 NH₂:NCO. Diethyl toluene diamine has also been used as the curingagent for ophthalmic lens applications.

[0030] For improved optical product performance (such as resistance tosunlight and heat discoloration, and cosmetic color preferences), thehigh impact polyurethane material may be modified with the addition ofdyes, colorants, anti-oxidants, and ultraviolet (UV) and thermalstabilizers. For instance, WV stabilizers, UV absorbers, antioxidantsand dyes such as those commonly available from companies such as CibaGeigy may be added up to a few percent by weight to alter the color orenvironmental stability of the material. In one preferred mixture, up to1% each of Irganox 1010 (an anti-oxidant and thermal stabilizer), UVstabilizer Tinuvin 328, and UV absorber Tinuvin 765 (all from CibaGeigy) were added for improved lifetime stability.

[0031] Polarizer 104 may comprise a variety of different constructionsand materials. Such constructions include freestanding or non-laminatedpolarized films, films with removable protective sheeting, and filmswith outer permanent protective coatings or supportive plastic layers.

[0032] Surprisingly, the inventors found that the rapid exothermicpolymerization reaction of the present high impact polyurethane resultsin good adhesion to polarizer wafers. Typically used with thermoplasticparts, wafers comprise protective plastic layers on one or both sides ofa polarizer film to increase the environmental durability and ease inhandling of the polarizers. Three layer wafer constructs sandwich thepolarizing film for protection and support on both surfaces. Two layerwafers (alternate material/polarizer film) may provide a supportinglayer on one surface, or a single protective covering toward the outersurface of the optical part. Wafers, however, being thicker and usuallylaminated often do not conform to highly curved or non-symmetricallycurved shapes and subsequently separate at the lamination interfaces dueto stress fracturing. In addition, such wafers may require the muchhigher temperatures of thermoplastic processing in order to conform tosuch shapes, or to join reliably with the introduced lens materials.Thermoplastic molding temperatures are commonly in the range of 260-320°C. rather than the 70-130° C. used in thermoset resin casting. Due tothe foregoing deficiencies, wafers are not commonly used with thermosetresins.

[0033] The inventors thus were unexpectedly surprised to discover thatpolarizer 104 may also be a wafer construct. Preferably, the wafer is apolycarbonate/PVA/polycarbonate layered combinations less than 1 mmthick. While such wafers are used in high temperature thermoplasticpolycarbonate lens molding, the inventors believed such a wafer wouldhave a lack of conformity and a high degree of delamination in thepresent lower temperature application. Such concerns were heightenedbecause the polycarbonate outer layer and the disclosed high impactpolyurethane are inherently dissimilar materials. Materials other thanpolycarbonate for the wafer construct may also comprise poly(methylmethacrylate), polystyrene, cellulose acetate butyrate (CAB), celluloseacetate, and cellulose triacetate.

[0034] With respect to materials of a freestanding polarizing film,these preferably include polyethylene terephthalate (PET) films,although PVA films may be used. PET polarizers, as disclosed in U.S.patent application Ser. No. 09/475,424 and hereby incorporated byreference, are preferred because they are stable and exhibit lowbirefringence, among other beneficial properties. Notwithstanding PET'spotential advantages, the inherent inertness of PET should be overcomefor the manufactured optical product to have adequate structuralintegrity. Thus, to effectively incorporate PET film as polarizer 104,methods to overcome PET's inertness for bonding should be employed. Suchmethods are, fully disclosed in the above-identified patent applicationand U.S. patent application Ser. No. 09/567,711, which application ishereby incorporated by reference.

[0035] Other polarizing films may include thin, multilayered polymericmaterials, combined reflective and dichroic polarizers, or films ofmixed polymeric phases such as those described in U.S. Pat. Nos.5,882,774; 6,096,375, and 5,867,316, and references respectively citedtherein, all of which are incorporated herein by reference.

[0036] Polarizer 104, as detailed below, may be protected by a varietyof permanent coatings applied to the outer surface to provide increasedresistance to scratches and environmental degradation.

[0037] Turning again to the drawings, FIGS. 3-6 illustrate variousproduction techniques for in situ solidification of the high impactpolymeric material against or around the polarizers, or subsequentbonding of the polarizer to a formed polymeric optical part. Thedisclosed and illustrated methods may effect a variety of optical partsthat include but are not limited to semi-finished lenses, finishedlenses, non-prescription lenses, facemasks, shields, goggles, visors,and display of window devices.

[0038] To elaborate, as shown in FIGS. 3-6, the exemplary manufacturingprocesses may yield a finished part ready for an intended opticalapplication. Alternately, they may yield an optical part in preparationfor further processing into another shape or for incorporation into alarger instrument or system. For example, the processes of FIGS. 3-6illustrate steps that can be used to form a finished polarized lensready for final insertion into a eyeglass frame, helmet or goggle; aprescription or non-prescription polarized lens blank to be edged tofinal shape and inserted into a frame; or a semi-finished polarized lensblank that must be surfaced, polished and edged to a final prescriptionand shape before being inserted into frames. Similarly, optical partsfor displays or windows could be prepared to final shape and size, ormanufactured via the processes of FIGS. 3-6 as large parts that aresubsequently cut, shaped, formed or further processed to final articles.

[0039] As illustrated in FIG. 3, the polarizer, such as polarizer 104,may be treated for improved adhesion at step “If desired, treat orcondition polarizer for adhesion improvement.” Previously reportedtreatments of polarizers, such as nitrocellulose coatings on CABpolarizer wafers (U.S. Pat. No. 3,833,289) and polyvinyl butyral coatingon polarizer sheets (U.S. Pat. No. 4,090,830), did not prove reliablefor ophthalmic lens processing. Therefore, the inventors investigatedalternate coatings, as well as chemical and/or physical treatments ofpolarizer films, for improved adhesion. Details of surface treatmentsand chemistries for improved bonding are disclosed in U.S. applicationSer. Nos. 09/475,424 and 09/567,711 mentioned previously. Suchtreatments include mechanical roughening, physical cleaning, chemicalsurface modification, plasma activation, and coating of the polarizers.

[0040] Treatments may be tailored to the chemical and/or physicalcharacteristics of the polarizer to be used, the polarizer's positionwithin the optical construct, such as construct 102, and the stage atwhich it is incorporated into the optical construct. For example, inFIG. 3; it may be appropriate or necessary to treat only the surfacethat will contact the polymeric material. In particular, single, innersurface treatment is preferred if the treatments of choice aremechanical roughening of a wafer polarizer, or high tack coating ofeither wafer or film polarizers.

[0041] At step 20 “Place polarizer against front surface of optical moldassembly,” the polarizer is advantageously positioned against onesurface (designated the front) of a mold assembly, such as a lens moldassembly. Thus, if a polarized wafer is used, for example, the resultingbenefit is that the outermost layer of the wafer becomes the frontsurface of the lens. This alone or with subsequent hard coating can givea lens with sufficient scratch resistance for front surface lensrequirements. Similarly, the polarizer film may be placed directly atthe front surface of the lens cavity if it is of a scratch-resistantmaterial, has been overcoated for protection, or is environmentallystable enough (such as the PET polarizer or certain constructs of thethin multilayer polarizers) to withstand subsequent direct use or hardcoating. This configuration can simplify the lens forming process.

[0042] Additionally, depending on what type of polarizer is used, thepositioning described in FIG. 3, can give enhanced optical performancebecause no optical loss due to refractive index mismatches, absorptionof additional materials, or birefringent randomization occurs before thepolarizer interacts with the light.

[0043] With the method illustrated in FIG. 3, the user may alsoadvantageously be able to apply positive or negative pressure againstthe polarizer to conform it against the front surface before or duringthe admission of the liquid-phase polymeric material. Such pressure maybe accomplished, for example, by using a gasket or cavity sealingmechanism such as that described in U.S. patent application Ser. No.09/447,445, which application is incorporated herein by reference as iffully set forth herein.

[0044] As detailed in that application and as illustrated in FIGS. 7 and8 herein, an exemplary sidefill gasket 212 is interposed betweenopposing mold members 202, 204 of a mold assembly 200 to define and seala lens chamber 214 within which a lens is to be cast. The gasket 212 maycomprise an annular body having a shoulder 220 formed on the insidesurface thereof. The shoulder 220 accommodates and seals the edges ofmold members 202, 204. The gasket 212, as exemplified by theillustrations of FIGS. 7 and 8, may further comprise a plurality of portholes 230, 232, 234 on the outside surface of the annular body. Eachhole 230, 232, 234 has a passageway 206, 208, 210 extending through theannular body of the gasket 212 and into the lens chamber 214. The portholes 230, 232, 234 and their respective passageways are adapted tocontrol the fill of the mold assembly (either with or without addedpressure) and exhaust any trapped gases produced during filling. Adelivery mechanism, such as needle 250, may be used to admit thepolyurethane-based material into the lens chamber 214.

[0045] An alternative to a gasket mechanism, such as that illustrated inFIGS. 7 and 8, may include a very fine hole made through the frontcavity surface, or a series of fine passageways made along the perimeterof the front surface, to pull the polarizer against the front surfacevia applied vacuum.

[0046] The optical mold assemblies employed in step 20 may comprisestandard glass molding surfaces, such as those in common practice forforming thermoset resin ophthalmic lenses. Alternately,reaction-injection molding (RIM) cavities may be used. Although RIMmolding technology has not previously been used to manufactureophthalmic lenses, the present high impact polyurethane-based materialis well suited to RIM manufacturing. Unlike traditional thermoset lens,technology, RIM molding technology may utilize multiple as well assingle cavities. Thus, the disclosed methods of manufacturing mayprovide a cost and production advantage over conventional individualthermoset lens cavity assemblies or techniques.

[0047] At step 30 “Admit optical material into assembly on back side ofpolarizer,” the optical material is introduced into the mold assembly.The high impact polyurethane-based material utilized in the preferredembodiments has a viscosity of approximately 1,000 centipoise. It iscommonly maintained prior to use as two pre-mixed components held atroom temperature (20-27° C.) and slightly elevated temperature (53-66°C.), respectively. When combined at the point of use, the mixtureexothermically reacts and begins to solidify within 30 seconds.

[0048] Since this reactive polymeric material solidifies so quickly, theinventors, through their initial failures, recognized that conventionaltechniques that depend on solidification lasting several hours could notbe used. In order for an acceptable optical-quality plastic part to beeffected, the inventors turned to one of their earlier inventions. Inparticular, the inventors turned to their sidefill gasket technologydisclosed in U.S. application Ser. No. 09/447,445. Sidefill gaskets andmethods as detailed therein incorporate extra vents to remove entrappedgases either by passive or active (e.g., vacuum) methods. A furtherrefinement may include automation for reproducible and accurate filling.

[0049] At step 30, the inventors prefer their sidefill gasket technologybecause it advantageously provides a means to remove trapped air fromthe mold assembly, as well as direct, and control the material'sintroduction into it, within the incredibly short thirty-second settime. With such a short set time, it is very easy to entrap bubbles inthe lens, which cause unacceptable defects in the final product. Inaddition, because of the quick set time, solidifying lens material islikely to draw back from inlet location and cause edge defects. Whilethe total percentage of material shrinkage may be less than otherthermoset materials, the evidence of shrinkage will be more obvious inany area, such as a fill port, where the material is unsupported in atleast one dimension and hence can shrink unevenly. Therefore, thesidefill technology also advantageously provides a reservoir of extramaterial that will flow into the inlet as it solidifies to minimize suchedge defects. Accordingly, by utilizing the inventors' unique sidefillgasket technology, a user may securably position the polarizer withinthe mold assembly, and then control and direct the liquid-phasepolymeric material on or around the polarizer during this criticalmanufacturing stage.

[0050] As shown in FIG. 3, while the polyurethane-based materialsolidifies quickly, the complete conversion to a stable final polymerrequires curing at step 40 “Cure optical part.” The cure processrequires several hours at, room temperature. A controlled elevatedtemperature, or a ramped increase to an elevated temperature, ispreferred for more reproducible production times and final optical andmechanical properties. Preferably, the elevated temperature ismaintained in the range of 110-130° C. Higher temperatures may result inyellowing of the material from reactive decomposition.

[0051] Two exemplary sequences for curing optical parts are:

[0052] 1. Fill cavity of the mold assembly at room temperature. Within10 minutes (when polymeric material has gelled to inhibit flow duringmovement), place the mold assembly in an oven at 121° C. Cure in moldassembly for 16-18 hours, then remove the optical part from theassembly; or

[0053] 2. Fill cavity of the mold assembly at room temperature. Placeassembly in oven at 121° C. for 3 hours. Remove optical part fromassembly and continue curing part in a 121° C. oven for an additional 15hours.

[0054] Step 40 may be the final step in the manufacturing process if theresultant part is sufficiently robust for its intended opticalenvironment. The polarizer chosen and the intended use of the partdetermine sufficient robustness. For instance, one could not use a PVApolarizer in the process of FIG. 3 and end the process at step 40 if thepart were exposed to water or high humidity in its intended use—thepolarized part would lose efficiency and the polarizer may deform ordelaminate under humid conditions. Moreover, as noted in the Backgroundof the Invention, supra, due to the high heat of reaction of thepolyurethane-based material, the PVA polarizer may be severely damagedsuch that the user may discover that use of this type of polarizer isnot advisable. For most applications, the inventors prefer PETpolarizing film, if it can be bonded according to the inventors'techniques disclosed in their earlier-identified applications, becausethis film can better withstand high heat compared to standard films suchas PVA films. Thus, depending on application, an outer PET polarizerlayer or polarized wafer may be sufficiently robust for expected wear.

[0055] As an option, additional scratch-resistant or hard coatings maybe preferred, as illustrated by step 60 “Apply additional coating(s) tosurface(s) of optical part.” Such coatings are normally applied toeyewear and other exposed optical parts to increase their lifetime instandard use or to enhance their optical properties. These coatings maybe applied to front, back, or all surfaces (including edges) as neededto protect or enhance the parts. Similarly, different coatings may beapplied to different surfaces (e.g., a scratch resistant coating on onesurface, and a tinted or mirror coating on another).

[0056] Several commercial coatings for enhanced scratch, rub and wearresistance, as well as increased environmental stability, are availablefor ophthalmic lenses or other optical parts. Such coatings may beapplied in the liquid state by roll, spin or dip coating, for example.Depending on the chemistry of the coating solution, the liquid film isconverted to a harder, solid layer by thermal, ultraviolet, infrared orother means of irradiation, reactive initiators or other reactivemethods. Vacuum-deposited coatings may be applied as an alternate to theliquid coating, or in addition to cured liquid coatings. Such vacuumcoatings may provide additional protection from physical wear,environmental degradation, or further control of the optical propertiesof the part. For instance, the liquid or vacuum deposited coatings mayalter light throughput in a particular energy region to giveanti-reflective or reflective (mirror) properties, alter the perceivedcolor of the part, or reduce exposure to emissions such as infrared orultraviolet emissions.

[0057] As shown in FIG. 3, coating step 60 may be the final step in thebasic manufacturing process. For the process outlined in FIG. 3, thefinal coating step 60 may provide preferred properties for optical partsconstructed with a variety of polarizers that include PET films, PVAfilms, multilayer polarizers, and wafer polarizers.

[0058]FIG. 4 illustrates a manufacturing process that positions thepolarizer within the bulk of the optical part. This manufacturingapproach may be used for better environmental and wear protection fordelicate polarizers (such as PVA films) or for demanding applications.For example, certain applications may benefit uniquely from protectingthe polarizer securely within the impact resistant polymeric material.These could include safety or shielding helmets, goggles, or glasses, ordisplay and window applications that may be subjected to high wind,pressure, vacuum, or other harsh conditions.

[0059] Step 10, as previously discussed, allows treatment, conditioning,coating or other preparations of the polarizing medium for enhancedadhesion and/or integral bonding within the optical part. In thismanufacturing process, it may be most preferred to prepare both surfacesof the polarizer for improved adhesion. This can be accomplished, forexample, by dip coating for a liquid surface treatment, by simultaneousor sequential exposure for irradiation treatment, and by sequential orsimultaneous physical roughening, cleaning, or conditioning of thesurface.

[0060] At step 22 “Position polarizer within optical part moldassembly,” the polarizer is positioned and supported within the moldassembly such that liquid-phase polymer material may be introduced onboth sides of the polarizer. This means that the polarizer is notresting against either of the outer molding surfaces. The inventors'gasket assembly disclosed in U.S. application Ser. No. 09/447,445 is asuitable gasket that may be used to support and securely position thepolarizer within the thickness of such an assembly. Depending on thefinal use of the optical part, the polarizer may be positionedequidistantly from each outer molding surface, or nearer one surfacethan the other. For example, to form a semi-finished ophthalmic lensblank, (commonly 6-15 mm total thickness), it is preferable to positionthe polarizer within 1.5 mm to 0.5 mm of the front molding surface. Thisensures that the lens blank can be ground to prescription withoutcutting into the polarizer, even for lenses with a final centerthickness of 2.2 to 1.8 mm. However, for display or non-prescriptioneyewear applications, it may be-preferable to place the polarizerequidistant within the optical part for optimal protection on both sidesof the polarizer.

[0061] To form the optical polarized part illustrated in FIG. 4,liquid-phase polymeric material is introduced on both sides of thepolarizer at step 32. The disclosed gaskets of U.S. application Ser. No.09/447,445 advantageously allow simultaneous introduction of material onboth sides of the polarizer layer, thereby preventing displacement ofthe polarizer as the material quickly reacts and hardens. Such a methodof controlled simultaneous introduction is preferred with this quicklysolidifying material to avoid flow lines or voids against the polarizerlayer that would degrade the optical performance. Similarly, the fillingthrough-hole(s) of these gaskets may be specifically designed to admitequal or differential distribution of the material around the polarizer,as required to achieve equal or dissimilar thicknesses of polymericmaterial on the front and back surfaces of the polarized optical part.As in FIG. 3, the through-holes also offer an important advantage inproviding reservoirs of material to ensure fully filled parts even uponreactive shrinkage, and to allow passages for egress of gases.

[0062] Step 40 “Cure optical part” is identical to the previous process,and may be the final, manufacturing step for some optical parts. SinceFIG. 4 illustrates a process that encapsulates the polarizer, this mayyield a sufficiently robust part with PET, wafer and even the moreenvironmentally sensitive PVA type polarizers.

[0063] Alternately, step 60 may be employed to place additionalprotective or property-enhancing coatings on one or more surfaces of theoptical part. Again, this would be a suitable process step for use witha wide range of polarizers, including PET, multilayer polymer, wafer,and PVA-type polarizers.

[0064]FIG. 5 illustrates a manufacturing process for two-sidedsequential fill of an optical-quality polarized part. The first threesteps are consistent with those previously defined and delineated.However, in this case, the front surface is a “dummy” surface thatdefines only an intermediate position within the final manufacturedoptical part. In this approach, the “dummy” surface gives added supportto the polarizer that might otherwise be displaced by the viscous lensmaterial; this can be especially useful for thin (e.g., film polarizersof less than 0.2 mm thickness) or fragile materials.

[0065] At step 30 “Admit liquid polymeric material behind polarizer tofill back of mold,” the liquid polymeric material is introduced onlybehind the polarizer to press it against the front surface. Again,active or passive means to assist conformance of the polarizer to thissurface may be included such as a gasket disclosed by U.S. applicationSer. No. 09/447,445.

[0066] At step 42, the polymeric material is cured in this sub-assemblyeither until totally reacted, or until a predetermined, sufficientlystable product is achieved. This can be a reasonable production processbecause the present polymeric material solidifies much more quickly thanstandard thermoset resins. Preferably, the part is cured to the pointwhere changes in mechanical stresses and physical dimensions have begunto plateau; if too short a period (10-15 minutes) is employed, thematerial will be too brittle when removed from the assembly and maycrack. A stable plateau may be reached in 1-3 hours, rather than the 10or more hours required with standard thermoset resins.

[0067] At step 44, the front “dummy” surface is removed, and a newsurface is positioned and held at a fixed distance from the totally orpartially cured subassembly. For an ophthalmic lens, the new surfacewould be preferably positioned 0.5-1.0 mm above the polarizer. Dependingon the design of the optical part, one may use either the same side fillgasket as in step 20, or another gasket that may differ from the firstgasket in depth, or number and position of through-holes.

[0068] The new surface in step 44 may have a contour identical ordifferent from the previous “dummy” surface,. For example, the followingapproach could be useful for an optical part with a modulated surface,such as an ophthalmic progressive lens, or a stepped surface such as anophthalmic bifocal lens. The “dummy” surface could approximate anintermediate curve between a spherical surface and the final surface.Hence the polarizer would be positioned more evenly with respect to thefinal front surface than if a standard spherical approximation wereused. For instance, in a high add power bifocal lens, the displacementin position of the front surface between the distance and readingportion of the lens may be 2 mm or more. A dummy surface could bedefined that, for example, allows a 1 mm displacement of the polarizerin the reading portion of the lens to position the polarizer closer tothe final front surface.

[0069] In step 46 “Admit liquid polymeric material into the front spacecreated by this second assembly,” liquid-phase polymeric material isthen directed into the newly defined cavity formed by the totally orpartially cured sub-assembly and the second, front molding surface. Theadditional liquid-phase polymeric material is introduced into thatcavity to sequentially form the front surface of the lens.

[0070] The final portion of the optical part is then cured at step 48,and the process is either completed at this stage or may be furtherenhanced by additional coatings consistent with the previously-discussedstep 60.

[0071] This sequential filling process is best suited for-use with thinor flexible polarizers, such as those comprising PET, PVA, or themultilayer polymer constructs. PET may be the most preferred forintermediate shaping because of its good conformal properties. However,even the wafer polarizers may be used in this manufacturing approach, ifdesired.

[0072]FIG. 6 illustrates a manufacturing process for bonding a PETpolarizer to an existing, solid optical part comprised of the presenthigh impact polyurethane-based material. Hence, FIG. 6 begins with thestep of “Obtain solid optical part of this high impact optical qualitypolymeric material.” In step 10, the PET polarizer may be treated forimproved adhesion, as discussed above in conjunction with theembodiments illustrated in FIGS. 3-5. One or both surfaces may betreated depending on whether the PET polarizer will form the outersurface (one-sided treatment preferred) or undergo further coating.

[0073] Steps 52 and 54 define two different methods to combine the solidoptical part or construct with the PET polarizer. In step 52, an opticaladhesive is used to bond the polarizer to the optical part's surface. Atwo part optical adhesive such as HE 17017 available from HartelsPlastics may be used. Step 54, in contrast, involves the reactivetreatment or modification of the optical part to effect adhesion to thepolarizer. This is a less preferred approach because such treatment maydamage the optical quality of the part (e.g., etching leads to surfaceroughness and scatter) or the physical integrity of the part (e.g.,chemical or physical surface and subsurface damage weakens the parttoward later chemical or environmental resistance).

[0074] For applications with limited handling and exposure, bonding astable polarizer, for example the PET-type polarizer, to the existingpart may be the final step in this manufacturing process. If morewear-resistance is required, coatings may be added in step 60 followingeither bonding process.

[0075] As evidenced by the range of manufacturing processes disclosedherein, many variations are possible which remain within the scope andconcept of the invention. The following examples are thus intended as,illustrations only since modifications within the scope of the generaldisclosure will be apparent to those skilled in the art.

EXAMPLES

[0076] For convenience and economy, thermoset mold assemblies were usedin the following examples.

[0077] Adhesion of the lens/film combination was evaluated by cutting anarrow cross-section of the lens, scoring into the lens from the backalmost to the front surface, and then breaking the lens along the scoreline to determine where adhesion is lost. In a few instances, theintrinsic cohesiveness of the polarizer was exceeded before the lensdelaminated. This means that a very strong bond was achieved. For weakerbonds, adhesion failure often occurs at the interface between thepolarizer and one of its protective layers (for a wafer construct), orbetween the polarizer and the main lens surface.

Example 1

[0078] A conventional thermoset mold cavity was assembled with a PVApolarizer film mounted within the lens cavity. High impactpolyurethane-based material was introduced into the cavity and allowedto flow around the polarizer. The lens was allowed to solidify at roomtemperature for a duration less than 10 minutes (until mixture gels).The lens was allowed to continue its reactive cure at 121 C. for 16hours.

[0079] Results: Polarizer type Displacement of polarizer? Adhesion a.PVA polarizer film, Yes — unacceptable treated for adhesion

Example 2

[0080] This example is representative of the manufacturing methodillustrated in FIG. 3. A thermoset mold cavity was assembled with thepolarizer resting against the front mold surface. Using a sidefillgasket, design as disclosed in U.S. application Ser. No. 09/447,445,wherein the gasket has vent holes in addition to a filling port,liquid-phase polyurethane-based material was admitted to only the regionof the assembly behind the polarizer film. The lens was allowed tosolidify at room temperature for a duration less than 10 minutes (untilmixture gels). The lens was placed in an oven to continue its reactivecure at 121° C. for 16 hours.

[0081] Results: Displace- ment of Polarizer type polarizer? Adhesion a.PET polarizer film UV No Delaminated with edge treated on back surfaceonly pressure b. PET polarizer, untreated No Poorer adhesion than a. c.PC/PVA/PC wafer No Yes — PASSED TEST

Example 3

[0082] This example is representative of the manufacturing methodillustrated in FIG. 4. A thermoset mold cavity was assembled with apolarizing layer using a sidefill gasket design as disclosed in U.S.patent application Ser. No. 09/447,445. Specifically, a slot-shaped porthole acted as the fill port to introduce, in a controlled manner, thethermosetting resin material along the edge axis of the embedded layer.Two port holes functioning as vent holes were located above the edgeaxis of the embedded material, i.e., on the thinner side of the lens toallow egress of any gases from the front surface of the lens. Anadditional vent port was located below the edge axis of the embeddedmaterial on the thicker side of the lens to allow egress of any gasesfrom the back lens surface. A curved fill nozzle designed to match theslot-shaped fill port was used to introduce material into the cavityaround the polarizing layer until the cavity was full and a small amountof material flowed out of the egress holes. After standard curing as inExample 1, the gasket was removed.

[0083] Results: Polarizer type Displacement of polarizer? Adhesion a.PVA polarizer film Yes — still unacceptable Yes

[0084] No gas bubbles were entrapped in the lens during thismanufacturing process.

Example 4

[0085] This example is representative of the manufacturing methodillustrated in FIG. 5. A thermoset mold cavity was assembled with thepolarizer resting against the front mold surface. Using another sidefillgasket design as disclosed in U.S. patent application Ser. No.09/447,445, liquid-phase polymeric material was admitted to only theregion of the assembly behind the polarizer film. This material wasallowed to solidify for ten minutes, then the front mold surface wasremoved and another mold surface spaced 1 mm away from the polarizerfilm was placed in the assembly. Resin was then inserted into this newlyformed front lens region to cover the front surface of the polarizer andassume the new front curvature of the lens cavity.

[0086] Results: Polarizer type Displacement of polarizer? Adhesion a.PVA polarizer film Yes — unacceptable Yes

[0087] The back lens portion (that formed first) cracked. This resultmay have been due to uneven pressures on the assembly during removal andreplacement of the front molding surface. A longer intermediate curingcycle may be advisable.

[0088] Accordingly, a new family of polarized optical-quality plasticparts comprised of high impact, lightweight, high optical qualitypolymeric material, and methods of manufacturing such parts, aredisclosed. While preferred embodiments are disclosed herein, manyvariations are possible which remain within the concept and scope of theinvention. Such variations would become clear to one of ordinary skillin the art after inspection of the specification and drawings herein.The inventions therefore are not to be restricted except within thespirit and scope of the appended claims. TABLE 1 Desired MaterialAttributes Lightweight = THIN - High Good Optical Safety = Lens LowDensity Refractive Quality = High High Impact Material (g/cm3) IndexAbbe Number Resistance Glass 2.2-2.54 1.45-1.7  64-67 Low, unless (best)thick (heavy) PMMA 1.19 1.491 57 Marginal (Acrylic) CR-39 ® 1.32 1.49858 Marginal or Hard Resin Poly- 1.2 1.586   30-34.5 High carbonateMid-index 1.2 1.52-1.56 35-43 Marginal Plastics High 1.3-1.4 1.59-1.6732-41 Marginal Index (best) Plastics Inventors' 1.11 1.53    45.5 HighModified (best) Polymeric Material

What is claimed is:
 1. An optical-quality polarized part comprising: an optical construct comprising a high impact polyurethane-based optical material; and a polarizer integrally bonded to the optical construct.
 2. An optical-quality polarized part according to claim 1 wherein the polarizer comprises a polyethylene terephthalate film.
 3. An optical-quality part according to claim 1 wherein the polarizer comprises a wafer.
 4. An optical-quality polarized part according to claim 1 wherein the polarizer comprises at least one layer supporting a polyvinyl alcohol film.
 5. An optical-quality polarized part according to claim 1 wherein the optical construct is a lens substrate.
 6. An optical-quality polarized part according to claim 1 wherein the high impact polyurethane-based optical material comprises a polyurethane prepolymer reacted with a diamine curing agent.
 7. An optical-quality polarized part according to claim 6 wherein the high impact polyurethane-based optical material further comprises a dye or colorant, a stabilizer, or a stiffener.
 8. An optical-quality polarized part according to claim 6 wherein the prepolymer comprises up to about 12 molar percent trimethylol propane.
 9. An optical-quality polarized part according to claim 6 wherein prepolymer is reacted with the diamine curing agent in an equivalent ratio of about 0.9 to 1.1 NH₂/1.0 NCO.
 10. An optical-quality polarized part according to claim 1 wherein the high impact polyurethane-based optical material comprises the reaction product of (a) a polyurethane prepolymer prepared by reaction of methylenebis(cyclohexyl isocyanate) with an OH-containing intermediate having a weight average molecular weight between about 500 and about 1,200 selected from the group consisting of polyester glycols, polyether glycols, and mixtures thereof in an equivalent ratio of 2.5 to 4.0 NCO/1.0 OH and (b) an aromatic diamine curing agent in an equivalent ratio of about 0.9 to 1.1 NH₂/1.0 NCO.
 11. An optical-quality polarized part according to claim 1, further comprising a hard coating, wherein the hard coating is integrally bonded to the optical construct.
 12. An optical-quality polarized part according to claim 1, further comprising a hard coating, wherein the hard coating is integrally bonded to the polarizer.
 13. A method of manufacturing an optical-quality polarized part comprising: forming a high impact polyurethane-based optical construct utilizing a sidefill gasket; and bonding a polarizer to the construct.
 14. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the optical construct is formed by placing liquid-phase polymeric material about one side of the polarizer.
 15. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the optical construct is formed by placing liquid-phase polymeric material about each side of the polarizer.
 16. A method of manufacturing an optical-quality polarized part according to claim 15 wherein the liquid-phase polyteric material is placed simultaneously about each side of the polarizer.
 17. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the polarizer is bonded to the optical construct after the optical construct has been formed.
 18. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the polarizer comprises a polyethylene terephthalate film.
 19. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the sidefill gasket has sidefill ports for admitting liquid-phase polymeric material via the sidefill ports onto at least one side of the polarizer.
 20. A method of manufacturing an optical-quality polarized part according to claim 13 wherein the optical construct is a lens formed with the polarizer at or near a front surface of the lens.
 21. A method of manufacturing an optical-quality polarized part according to claim 13 further comprising the step of treating the polarizer for integral, bonding to the optical construct.
 22. A method of manufacturing an optical-quality polarized part according to, claim 19 further comprising the step of treating the polarizer for integral bonding to the optical construct.
 23. A method of manufacturing a polarized lens comprising: positioning a polarizer within a mold cavity; admitting liquid-phase high impact polyurethane-based optical material into the mold cavity; and forming a solid lens with the polarizer at or near a front surface of the lens, wherein the polarizer comprises a polyethylene terephthalate film.
 24. A method of manufacturing a polarized lens according to claim 23 wherein the polarizer is positioned within the mold cavity via a sidefill gasket.
 25. A method of manufacturing a polarized lens according to claim 23 further comprising treating the surface of the polarizer for applying a hard coating thereon and applying the hard coating to the film.
 26. A method of manufacturing a polarized lens according to claim 23 further comprising treating the surface of the polarizer for integral bonding to the lens.
 27. A method of manufacturing a polarized lens comprising: positioning a polarizer within a mold cavity; admitting liquid-phase high impact polyurethane based optical material into the mold cavity; and forming a solid lens with the polarizer at or near a front surface of the lens, wherein the polarizer comprises a wafer.
 28. A method of manufacturing a polarized lens according to claim 27 wherein the polarizer is positioned within the mold cavity via a sidefill gasket.
 29. A method of manufacturing a polarized lens according to claim 27 further comprising treating the surface of the polarizer for applying a hard coating thereon and applying the hard coating to the film.
 30. A method of manufacturing a polarized lens according to claim 27 further comprising treating the surface of the polarizer for integral bonding to the lens. 